The magnetocaloric effect and critical behaviour of the Mn0.94Ti0.06CoGe alloy

P. Shamba, J. Lwang, J. C. Debnath, S. J. Kennedy, R. Zeng, M. F. Md. Din, F. Hong, Z. X. Cheng, A. J. Studer, S. X. Dou

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    Abstract

    Structural, magnetic and magnetocaloric properties of the Mn0.94Ti0.06CoGe alloy have been investigated using x-ray diffraction, DC magnetization and neutron diffraction measurements. Two phase transitions have been detected, at T-str = 235 K and T-C = 270 K. A giant magnetocaloric effect has been obtained at around Tstr associated with a structural phase transition from the low temperature orthorhombic TiNiSi-type structure to the high temperature hexagonal Ni2In-type structure, which is confirmed by neutron study. In the vicinity of the structural transition, at T-str, the magnetic entropy change, -Delta S-M reached a maximum value of 14.8 J kg(-1) K-1 under a magnetic field of 5 T, which is much higher than that previously reported for the parent compound MnCoGe. To investigate the nature of the magnetic phase transition around T-C = 270 K from the ferromagnetic to the paramagnetic state, we performed a detailed critical exponent study. The critical components gamma, beta and delta determined using the Kouvel-Fisher method, the modified Arrott plot and the critical isotherm analysis agree well. The values deduced for the critical exponents are close to the theoretical prediction from the mean-field model, indicating that the magnetic interactions are long range. On the basis of these critical exponents, the magnetization, field and temperature data around T-C collapse onto two curves obeying the single scaling equation M(H, epsilon) = epsilon(beta)f +/- (H/epsilon(beta+gamma)).
    Original languageEnglish
    Article number56001
    Number of pages7
    JournalJournal of Physics. Condensed Matter
    Volume25
    DOIs
    Publication statusPublished - 2013

    Keywords

    • magnetic entropy
    • nickel
    • temperature
    • transitions

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